I have three broad goals for the period of requested support. The first is to continue work on a general theory of development based on dynamic systems principles. The theory seeks to describe, and hopefully, to model, developing organisms as multicomponent systems, where the elements of the system are coupled in parallel, and where the resulting behavior obeys the general principles of nonlinear dynamics. Plans for professional growth include tutorial and collaboration with scientists working on dynamic and connectionist models in motor control and cognition. The second goal is a program of research devoted to understanding an aspect of skill development in infancy. This research, in collaboration with a leading biomechanist, Dr. Ronald F. Zernicke, of UCLA, seeks to understand how infants harness and optimize the forces associated with moving their limbs and body segments, a process believed to be essential in acquiring skill. A systems- functionalist theoretical framework is used to generate questions about the development role of these so-called intersegmental dynamics. 1. How are the moments of force partitioned among the body segments in newborn infants? 2. How do limb dynamics change with and affect, task? 3. How do limb dynamics change with age? 4. What is the effect of posture on skill acquisition? 5. What are the underlying patterns of muscle activities in common infant actions? 6. How do perturbations of movement affect limb dynamics? Infants in a longitudinal and several cross-sectional studies will have their movements recorded by a computerized motion-analysis system, and kinematic and kinetic measures of limb coordination, control, and distribution of energy will be determined. These studies have important implications for understanding skill development: 1. They describe, for the first time, how forces are apportioned among body segments as infants gain skill 2. They show how dynamical factors interact with other neural, structural, and contextual variables to determine skill performance. 3. They provide a principled basis for understanding how information about the individual's body and the external world can be transduced by the nervous system to produce action, and ultimately, developmental change. My final goal is to write the theoretical and empirical work in a monograph.